The present invention relates to an admixture or additive for cement or ready-mixed cement and more specifically to an admixture effective as a setting accelerator, a rust proofing agent for reinforcing steel or a frost resistive agent for concrete and mortar as hydraulic cement blends.
As such a setting accelerator, there have in general been used a chlorine-containing compound, in particular, calcium chloride or chlorine-free compound in the form of a salt such as potassium thiocyanate or sodium carbonate. Moreover, nitrites as rust proofing agents for reinforcing steel and aliphatic aminoalcohols as frost resistive agents have been used as principal components for admixtures. In this connection, Japanese Un-Examined Patent Publication (hereinafter referred to as "J.P. KOKAI") No. Hei 1-17625 discloses amidosulfonic acid as an antifreezing agent or a hardening accelerator and J.P. KOKAI No. Hei 6-19955 discloses the use of an admixture composed of glycol which serves as a low temperature hardening accelerator.
However, the use of calcium chloride which has currently been employed as a setting accelerator or a frost resistive agent suffers from a problem such that the chlorine atoms present in the compound causes corrosion of steel materials embedded in concrete and that this leads to reduction in the strength and durability of the resulting concrete. For this reason, the use thereof has been regulated recently. In addition, the chlorine-free compounds such as potassium thiocyanate, sodium carbonate, sodium nitrite, formates and amidosulfonic acid, which have been used as substitutes for calcium chloride, exhibit reduced effect of corroding steel materials, but are inferior to calcium chloride in the degree of setting acceleration effect, strength achieved after hardening and price, while glycol does not have satisfactory effect when it is used alone. Therefore, there has been desired for further improvement of these additives.
On the other hand, the electroless nickel-plating technique has widely been used in various fields, in particular, in the electronic industries for plating, for instance, recording mediums. However, waste fluids generated during the processes have been disposed through ocean disposal or after chemical sewage treatments without effective reuse thereof except for a rare case wherein they are reused as chemical fertilizers.
In respect of treatments for the waste fluids originated from the electroless nickel-plating processes, however, the ocean disposal thereof has completely been prohibited because of the recent world-wide trend of terrestrial environmental protection. For this reason, there has been intensively desired for the development of an economical method for treating or reusing the waste fluids originated from the foregoing plating processes, which presently amount to not less than 20,000,000 l per year.